1. 4.1 Architecture of the GSM system GSM is a PLMN (Public Land Mobile Network) – several providers setup mobile networks following the GSM standard within each country – components MS (mobile station) BS (base station) MSC (mobile switching center) LR (location register) – subsystems RSS (radio subsystem): covers all radio aspects NSS (network and switching subsystem): call forwarding, handover, switching OSS (operation subsystem): management of the network

2. 4.2 GSM: Architecture NSS MS BTS BSC GMSC IWF OMC BTS BSC MSC A bis UmUm EIR HLR VLR A BSS PDN ISDN, PSTN RSS radio cell MS AUC OSS signaling O

3. 4.3 UmUm A bis A BSS radio subsystem MS BTS BSC BTS BSC BTS network and switching subsystem MSC fixed partner networks IWF ISDN PSTN PSPDN CSPDN SS7 EIR HLR VLR ISDN PSTN GSM: system architecture

4. 4.4 System architecture: radio subsystem Components – MS (Mobile Station) – BSS (Base Station Subsystem): consisting of BTS (Base Transceiver Station): sender and receiver BSC (Base Station Controller): controlling several transceivers Interfaces – U m : radio interface – A bis : standardized, open interface with 16 kbit/s user channels – A: standardized, open interface with 64 kbit/s user channels UmUm A bis A BSS radio subsystem network and switching subsystem MS BTS BSC MSC BTS BSC BTS MSC

5. 4.5 System architecture: network and switching subsystem Components oMSC (Mobile Services Switching Center): oIWF (Interworking Functions) oISDN (Integrated Services Digital Network) oPSTN (Public Switched Telephone Network) oPSPDN (Packet Switched Public Data Net.) oCSPDN (Circuit Switched Public Data Net.) Databases oHLR (Home Location Register) oVLR (Visitor Location Register) oEIR (Equipment Identity Register) network subsystem MSC fixed partner networks IWF ISDN PSTN PSPDN CSPDN SS7 EIR HLR VLR ISDN PSTN

6. 4.6 Radio subsystem The Radio Subsystem (RSS) comprises the cellular mobile network up to the switching centers Components – Base Station Subsystem (BSS): Base Transceiver Station (BTS): radio components including sender, receiver, antenna - if directed antennas are used one BTS can cover several cells Base Station Controller (BSC): switching between BTSs, controlling BTSs, managing of network resources, mapping of radio channels (U m ) onto terrestrial channels (A interface) BSS = BSC + sum(BTS) + interconnection – Mobile Stations (MS)